This transgene consists of SV40 small T antigen in a reverse orientation, a 900 bp fragment of the Amy2 promoter region, cre recombinase, and a human growth hormone mini gene. Cre expression is seen in the definitive endoderm starting at E9.0 but is not seen in the liver or ventral pancreas before E12.5. The integration site was mapped to chromosome 15 in the promoter region of Zhx1.